docs: def _filter_matrix_columns(cls, matrix, phandango_header, csv_header):
          '''phandango_header, csv_header, matrix = output from _to_matrix'''
          indexes_to_keep = set()
  
          for row in matrix:
              for i in range(len(row)):
                  if row[i] not in {'NA', 'no'}:
                      indexes_to_keep.add(i)
  
          indexes_to_keep = sorted(list(indexes_to_keep))
  
          for i in range(len(matrix)):
              matrix[i] = [matrix[i][j] for j in indexes_to_keep]
  
          phandango_header = [phandango_header[i] for i in indexes_to_keep]
          csv_header = [csv_header[i] for i in indexes_to_keep]
          return phandango_header, csv_header, matrix